The present invention relates to a magnetic thin film and a method for forming the magnetic thin film, more specifically to a magnetic thin film having a high specific resistance value and a method for forming the magnetic thin film.
Conventionally magnetic thin films, which have good soft magnetic characteristics, have been used as the magnetic cores for use in thin-film magnetic devices, such as thin-film magnetic heads, thin-film transformers, thin-film inductors, etc.
Magnetic thin films of especially Permalloy (iron-nickel alloy) are widely used as upper magnetic cores, etc. of recording heads of hard disk devices because of their high magnetic permeability, good soft magnetic characteristics and low magneto striction.
However, magnetic thin film of Permalloy, a specific resistance value of which is as low as about 20 .mu..OMEGA.cm, has large loss for high-frequency magnetic fields of above 10's MHZ due to eddy current, which makes it difficult that the magnetic thin film can have good high-frequency characteristics.
Then techniques for forming magnetic thin film of high specific resistance values by mixing Mo (molybdenum) in Permalloy have been proposed.
In Japanese Patent Laid-Open Publication No. 122426/1995, for example, discloses a multi-layer film formed of a layer having a larger Mo mixed amount and a higher specific resistance value and a layer having a smaller Mo mixed amount laid sequentially one on the other. It is described that such multi-layer Permalloy film has good soft magnetic characteristics. Such multi-layer film is formed by electric plating using a bath with Mo ions added, and the Mo mixed amounts in the magnetic thin films are adjusted by changing a current density. It is described that tartaric acid is added to the Permalloy bath so as to largely change Mo mixed amounts in the magnetic thin films.
Japanese Patent Laid-Open Publication No. 63016/1997 discloses a magnetic thin film formed of Permalloy containing molybdenum, chrome and tungsten. It is described that such magnetic thin film has an above 1.5 T (tesla) saturation magnetic flux density, a below 1.0 Oe (oersted) coercive force Hc and an above 40 .mu..OMEGA.cm specific resistance value.
However, Japanese Patent Laid-Open Publication No. 122426/1995 and Japanese Patent Laid-Open Publication No. 63016/1997 do not disclose at all how to suitably control an Mo mixed amount to be introduced into magnetic thin film. Magnetic characteristics of magnetic thin film of Permalloy tends to much change by an Mo mixed amount. It is very important to establish a technique for suitably controlling an Mo mixed amount.